Set all ingredients out ahead of time and allow to come to room temperature

Put egg yolk, apple cider vinegar, lemon juice, dry mustard, sea salt and cayenne into the bottom of a wide mouthed mason jar or a bowl

Very slowly, just a few drops at at time, add the oil and blend or whip. If you add too much at once the mayonnaise will separate rather than emulsify

Once half of your oil is added you may add the remaining oil a bit quicker until all is blended and mayo is thick and creamy.